High Power Microwave Device Applications for New Narrow Resonance Linewidth Planar Hexagonal Ferrites

摘要

A ferromagnetic resonance linewidth of 3.8 oersteds at 9.0 kMc and room temperature represents a considerable improvement in material technology for hexagonal ferrites with planar anisotropy. The linewidth compares favorably with that found in single-crystal YIG and in lithium ferrite. This investigation has shown that the large planar anisotropy endows ZnY materials with several distinct advantages in enhancing the design of microwave devices. The anisotropy field increases the frequency range for the coincidence of the first- and second-order processes, which inherently gives a lower threshold power level. In addition, the anisotropy field tends to decrease the critical field (power level) at which spin-wave instabilities set in. From the measured threshold field, a spin-wave linewidth of 0.74 oersteds has been calculated for manganese-substituted ZnY. A variety of investigations on the feasibility of microwave devices using manganese-substituted ZnY are currently in the design stage. Among them are an orthogonal resonant strip-line gyromagnetic limiter at X-band frequencies, a parallel pumped shunt arm cavity limiter at K sub-band frequencies, and a TE101 cavity subsidiary resonance limiter. (Author)